As a media-circulation type pulverizer, there has been known a media-agitation mill proposed in JP 2005-199125 A.
The media-agitation mill proposed in the JP 2005-199125 A comprises: a pulverization tank including an end plate closing up an upper end thereof and internally having a pulverization chamber containing pulverizing media; a rotary shaft rotatably provided in the pulverization tank; and an agitating/separating member provided on a portion of the rotary shaft located inside the pulverization chamber and configured to be rotatable integrally with the rotary shaft. This media-agitation mill is characterized in that an inner wall surface of the pulverization chamber and an outer peripheral surface of the agitating/separating member are formed in shapes conforming to each other, wherein the media-agitation mill further comprises a separation/discharge passage extending from the outer peripheral surface of the agitating/separating member to penetrate through a central portion of the agitating/separating member and then extending therefrom to penetrate through a central portion of the rotary shaft and communicate with an outside of the pulverization chamber, and a pressure relief hole penetrating between upper and lower surfaces of the agitating/separating member in an axial direction of the rotary shaft to provide communication between upper and lower regions of an inside of the pulverization chamber.
However, in the media-agitation mill having the above structure, the pulverizing media are liable to be concentrated around a maximum-diameter portion where a centrifugal force is maximized, i.e., to be localized in a specific position, so that a dispersion or pulverization force varies with position, and the variation is large. Thus, there is a problem that a raw material is not uniformly dispersed or pulverized, causing difficulty in obtaining a high-quality product.
Therefore, the applicant of this application proposed a media-circulation type pulverizer capable of obtaining a high-quality product by a good pulverizing-dispersing action, in Japanese patent application No. 2009-103529 (JP 2010-253339 A).
The media-circulation type pulverizer proposed in this application comprises: a pulverization container having an upright cylindrical pulverization chamber containing pulverizing media in the form of beads; a raw-material-slurry supply port provided in the pulverization container; an agitating member disposed in a lower region of the pulverization chamber and having a rotary shaft substantially coaxial with a central axis of the pulverization chamber; and a media separation member provided within the pulverization chamber and above the agitating member. This media-circulation type pulverizer is characterized in that it further comprises a guide ring installed to radially divide a lower region of the pulverization chamber into an inner section and an annular outer section, thereby to form said outer section of the lower region of the pulverization chamber as an upward flow path of a mixture of pulverizing media and the raw material slurry.
In the media-circulation type pulverizer proposed in the Japanese patent application No. 2009-103529, the guide ring is installed in the pulverization chamber, as mentioned above, whereby a flow of the mixture of the pulverizing media and the raw material slurry can be formed as a combined flow (i.e., helicoidal flow) consisting of a flow moving in a circumferential direction of the pulverization chamber (i.e., a primary flow) and a flow capable of regularly repeating a movement cycle of, after moving in a radially outward direction of the pulverization chamber toward an inner wall of the pulverization container, moving upwardly through the upward flow path between the guide ring and the pulverization container, and then moving downwardly from a central region of the pulverization chamber to return to the agitating member, via a space inward of the guide ring (i.e., a secondary flow). Thus, even if a volume ratio of beads to the pulverization chamber is relatively low, segregation of the pulverization media can be suppressed to some extent to provide enhanced pulverization/dispersion efficiency.
However, the helicoidal flow formed by the media-circulation type pulverizer proposed in this patent application is unstable due to weakness and instability of the secondary flow thereof, so that due to centrifugal force, dynamic localization is likely to occur, which causes segregation of the pulverization media in the helicoidal flow. Thus, there is a problem of non-uniform pulverization and not-so-good energy efficiency.
Therefore, the applicant of this application proposed a media-circulation type pulverizer capable of creating a uniformized, stable helicoidal flow without dynamic localization due to centrifugal force in a mixture of pulverizing media and a raw material slurry, without unevenness of a centrifugal force distribution, thereby performing pulverization/dispersion uniformly with good energy efficiency, in JP 2014-018797 A.
The media-circulation type pulverizer proposed in the 2014-018797 A comprises: a pulverization container including an end plate closing up an upper end thereof and having an upright cylindrical pulverization chamber containing pulverizing media in the form of beads; a raw-material-slurry supply port provided in the pulverization container; an agitating member disposed in a lower region of the pulverization chamber and having a rotary shaft substantially coaxial with a central axis of the pulverization chamber; and a media separation member provided within the pulverization chamber and above the agitating member. This media-circulation type pulverizer is characterized in that it further comprises: a guide ring installed to radially divide a lower region of the pulverization chamber into an inner section and an annular outer section, whereby a flow of a mixture of the raw material slurry and the pulverizing media is formed as a helicoidal flow comprising a combination of a primary flow flowing in a circumferential direction of the pulverization chamber and a secondary flow flowing through a circulation flow path which has an upward flow path and a downward flow path created, respectively, in the outer section and the inner section of the lower region of the pulverization chamber, with respect to the guide ring; and rotational-flow suppressing means provided within the pulverization chamber and configured to suppress the primary flow while strengthening the secondary flow, thereby stabilizing the helicoidal flow, wherein the rotational-flow suppressing means is formed in a cruciform shape and provided inside the guide ring, and the guide ring provided with the rotational-flow suppressing means is disposed above the agitating member.
In the above media-circulation type pulverizer, regarding the helicoidal flow of the mixture of the raw material slurry and the pulverizing media, it becomes possible to suppress the primary flow of the helicoidal flow, i.e., a rotational flow in the circumferential direction of the pulverization chamber, and strengthen the secondary flow of the helicoidal flow (circulation flow around the guide ring). This makes it possible to stabilize the helicoidal flow and uniformize distribution of the pulverizing media in the flow to provide a flow having highly repetitive shear optimal to pulverization/dispersion with good energy efficiency.